Mode of Stimulation by Aldosterone of the Sodium Efflux in Barnacle Muscle Fibres: Effects of Ouabain, Ethacrynic Acid, Diphenylhydantoin, (ATPMg)(2-), Adenine Translocase Inhibitors, Pyruvate and Oxythiamine.

摘要

A study has been made of the nature of the delayed stimulation caused by external aldosterone in barnacle fibers pre-exposed to aldosterone. Microinjection of 0.5 M-ATPMg(2-) caused only a small but prompt rise in the Na efflux. Delayed stimulation was reduced whether ATP had been injected or not by prior external application of .0001M ouabain or internal application of .08M ethacrynic acid. It was completely abolished by prior application of ouabain externally and ethacrynic acid internally, or only .0001M diphenylhydantoin externally. Microinjection of atractyloside or bongkrekic acid caused a substantial fall in the resting Na efflux. Bongkrekic acid provided more powerful than atractyloside. Microinjection of 0.05 M-ATPMg(2-) into fibres poisoned with 2.0-X102M bongkrekic acid completely restored the Na efflux. Microinjection of .01M pyruvate caused a brief small rise in the rate constant for Na efflux and when followed by external application of aldosterone there was an enhanced delayed response. Microinjection of .01M oxythiamine caused a gradual fall in the resting Na efflux and abolished the delayed stimulation caused by external aldosterone. Fibres into which pyruvate had been injected when injected with oxythiamine behaved towards external aldosterone in the same was as control fibres injected with oxythiamine. Microinjection of phosphatidyl-L-serine (20 mg/ml.) before external application of aldosterone failed to result in an enhanced delayed response.